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Water Source Change, How to Manage Transition

Hi water experts, I have a pressing question:

My water company switched to groundwater about a month ago due to finding a parasite in our typical water source (bull run reservoir). The water properties are quite different, with Bull Run being much softer and lower in pH.

When the change to groundwater happened, it stressed my discus for a couple days as I did 50% daily changes. My concern now is, how to change back to Bull Run considering this time I will be going to a much lower pH, which I understand to be much more stressful for the fish.

Re: Water Source Change, How to Manage Transition

Sorry for a delayed response here Eric .
I wonder how did the transition end up ?
To tell you honestly with a PH diffrrence with a downward swing of 1.4 degree I would have gone with a lot less water changes than your initial 50% , but it seems that your discus ,on my amazement , have accepted the pH drop of 0.7 degrees just fine .

Re: Water Source Change, How to Manage Transition

Originally Posted by Filip

Sorry for a delayed response here Eric .
I wonder how did the transition end up ?
To tell you honestly with a PH diffrrence with a downward swing of 1.4 degree I would have gone with a lot less water changes than your initial 50% , but it seems that your discus ,on my amazement , have accepted the pH drop of 0.7 degrees just fine .

Hi Filip.

Yes, they were absolutely fine, swimming in the new water during the change. I did add two 1/2 tbsp doses of baking soda as I refilled the tank, which is my standard practice to add some KH to my tank. I think this helped.

Re: Water Source Change, How to Manage Transition

50% water at a pH of 6.0 + 50% water at a pH of 8.0 would equal a mixed value of a pH at 7.0.

However, this is not the case at all. Quite often mixing the two will result in a pH much higher than this, if there is a change at all.

I am actually quite surprised in this case it worked out that way, are you sure?

Quite right, since pH is logarithmic, the pH dropped slowly, especially adding the baking soda. 7.0 is where I have stabilized (its been a week since the OP), and where I typically ended up after adding 1 tbsp of baking soda per 60 gallons before the temporary water source change. This is why the fish tolerated it so well, the pH did not drop dramatically despite regular size water changes.

Re: Water Source Change, How to Manage Transition

50% water at a pH of 6.0 + 50% water at a pH of 8.0 would equal a mixed value of a pH at 7.0.

However, this is not the case at all. Quite often mixing the two will result in a pH much higher than this, if there is a change at all.

I am actually quite surprised in this case it worked out that way, are you sure?

This is an eye opener for me Rick .
I guess KH values play an important role on the final PH value when 2 different level PH water sources are mixed and it doesn't comes down to just doing a simple Math.

Re: Water Source Change, How to Manage Transition

When you mix water having a strong acid and a strong base, and there are no buffers involved, adding half pH 6 and half pH 8 would result in pH of 7. The H and the OH would combine to form water.

But natural water is different, it is buffered by carbonates and (mostly) bicarbonates. As you add the acidic water to the higher pH water, the carbonate alkalinity (KH) within the more alkaline water consumes the acid so that the pH will only go down slightly.

Re: Water Source Change, How to Manage Transition

When you mix water having a strong acid and a strong base, and there are no buffers involved, adding half pH 6 and half pH 8 would result in pH of 7. The H and the OH would combine to form water.

But natural water is different, it is buffered by carbonates and (mostly) bicarbonates. As you add the acidic water to the higher pH water, the carbonate alkalinity (KH) within the more alkaline water consumes the acid so that the pH will only go down slightly.

I'll actually get a white precipitate on the bottom of my tank if I go more than a couple days without a WC. I've always assumed it was the neutralized carbonates falling out of solution.